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Table of Contents

How Many Stars?

Local Illumination

In order to determine the quality of the nighttime sky, and to preserve your eye's dark adaption, it is important to seek a location in your neighbourhood that is away from the direct illumination of unshielded light sources.

The photographs below illustrate this point.

In cities it is difficult to avoid direct light since both street lighting and commercial lighting are very densely located even in residential neighbourhoods.

Poor Lighting Practices

Poor Lighting Practices

The following photos help to illustrate the effects of good and bad lighting practices.

The left photo shows the effects of unshielded and undirected light. The glare produces bright "washout" effects which obscure background objects and destroy one's night vision.

The practice wastes a lot of energy in the form of light which is directed upwards into the sky and contributes to an effect called "light pollution".

Better Lighting Practices

Better Lighting Practices

This photograph was exposed using the same criteria as the above photo, except that the deck light was shielded so that all the light was directed downwards.

The light is less intrusive and makes the area seem "warmer" and friendlier without the blinding glare.

Good ground level illumination can be achieved with less wattage when all of the light is directed downwards. This leads to considerable savings in electrical energy.

Much Better Lighting Practices

Much Better Lighting Practices

This photograph was exposed using the same criteria as the above photos but using only the natural light from the Moon.

The moonlight is quite bright and its light washes out the faint stars. The brightness of the moon is enhanced by the white snow on the ice covered lake.

IF POSSIBLE, PERFORM YOUR STAR COUNT OUT OF THE DIRECT LINE-OF-SIGHT TO UNSHIELDED LIGHT SOURCES AND CHOOSE A MOONLESS NIGHT

 

Prepared by YES I Can! Science Team at McMaster University,
for the Canadian Space Agency.